ABOUT THE EFFECT OF SUBSTITUTION ON THE C RYSTAL-STRUCTURE OF SRNI2P2

With several series of mixed crystals the effect of substitution on th e crystal structure of SrNi2P2 (polymorphic, the structures are varian ts of the ThCr2Si2 type) is investigated by X-ray methods. In the comp ound Ni completely can be substituted by Co and Cu respectively and al so P by As; in Sr1-xCaxNi2P2 there is a gap of the miscibility between 0.3 less than or equal to x less than or equal to 0.6. A low substitu tion of the several elements more than proportionally changes the stru cture parameters. In this range the mixed crystals with Ca, Cu, and As , respectively, undergo first order phase transitions with significant changes of the bond distances, which will be interpreted by the resul ts of band structure calculations.